This invention relates to vehicular exhaust system mufflers, and more specifically, to the joints of internal components of the mufflers.
Spot welding is commonly used in the fabrication of vehicular exhaust system mufflers. As evidenced by U.S. Pat. Nos. 2,367,753; 3,557,903; and 3,608,667, spot welding has long been considered less than perfect as a jointing technique. A variety of reasons exist. First, spot welded joints may be difficult to inspect. Second, spot welding may radically change the internal structure of the jointed members within and adjacent the spot welded joints. Third, spot welding may destroy the continuity of protective coatings on the jointed members. Fourth, joint member alignment may suffer due to material distortion during welding. Fifth, harmful metallic gases may be generated by spot welding, especially with galvanized materials. Sixth, time is required for spot welded joints to cool before further handling. For these and other reasons quality control, speed and safety may not be achieved to an extent desired. For these same reasons, mechanical joints have been attempted in the fabrication of vehicular exhaust system mufflers. Like welded joints, mechanical joints must provide acceptable, if not superior and excellent, tensile, compressive and torsional strengths between mated muffler components, as well as acceptable fatique life and an acceptable seal against gas leakage. While the foregoing patents disclose such attempts, to date, superior mechanical joints have remained unachieved in muffler fabrication.